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A Journal ofySE-UHE Radio Technology & Engineering 

111! f Pio^tlslied 

Pul^lMifeer^Sdlters Check* 

VolumeS, Number 4_ $5.0 

Here’s a promise you wish we’d break. 
So do we, but postal rate hikes and 
drastic increases for paper and other 
materials required to produce the WSR 
force our promise to up the subscription 
rates for the first time in history. It can’t 
be helped, but I think you’ll agree we 
held the line. So here’s the deal: 

Effective July 1,1995, the new rates will 
be etched into stone as follows: 


USA Foreign Surf 

Single issue $ 5.00 $ 5.50 

6-mos, 5-issues: $20.00 $25.00 

1- yr; 10-issues: $35.00 $45.00 

2- yr; 20-issues: $65.00 $75.00 

Sorry, Hackers, but we have to do it or 
dine at the local soup mission. We’ll 
offer current subscribers the chance to 

lock in the old rates for any of the three 
regular periods of 6-mos, 1-yr, or 2-yrs. 
Apologies to our Canadian and foreign 
readers who have to bite more of the 
bullet. Costs of postage, paper, and extra 
handling have to be passed on to 
everyone, pro-rata. When the new rates 
go into effect, a discount is built in for 
the longer sub periods. 

AGA Associates informs me that they 
are negotiating future volume purchases 
of the Metex M-3850 and other Metex 
multimeters and that our stated $179.95 
price is not necessarily carved into stone. 
Therefore, if you are interested in a 
computer-interfaceable data acquisition 
multimeter, give AGA Associates 
another call or opportunity to present 

Microsoft’s new operating system to 
replace Windows 3.1 and Windows For 
WorkGroups 3.11, formerly coded as 
“Chicago” and now called Windows 95 
seems solidly positioned for a long 
awaited August, 1995, release. 

I have been beta testing Windows 95 
since the Spring of last year, and am 

We remain committed to a program for 
continual improvement, too. Suggestions 
are welcome, of course, but barring 
unforeseen circumstances or better 
suggestions, we’re looking to upgrade 
our laser printing facility from the 
present 300-dpi to a 600/1200 dpi 
workhorse. I’d like to hear from anyone 
“in the business ” who might be able to 
make us a good offer for the Cause. 

Ultimate Scanner Book Price List 


After Junei-30^:1995 



their latest price and delivery quote: 

AGA Associates 
PO Box 99573 
Seattle, WA 98199-0573 
FAX (206) 217-9138 

AGA Associates is a progressive, 
forward thinking, new entry into the 
hacker and hobby scene. You’ve 
probably not heard of them before last 
month, but unless I miss my guess, you’ll 
see more and more of them in the 
coming months. Their Metex 
multimeters are hot performers and well 
worth the hacker’s second look. I am 
still ga-ga over their Windows 
Scope View control program! Wow! 

happy to report that I think it’s just about 
ready. In fact, Microsoft has already 
issued a “pre-release” version of 
Windows 95 on a first-come, first-served 
basis for $30. The “pre-release” is 
designed for corporate and serious users 
who need to plan ahead and cement their 
computing needs in advance of purchase. 

In case you didn’t know, Windows 95 is 
an immensely improved graphical user 
interface (GUI) over previous versions, 
and just about eliminates the much 
maligned MS-DOS operating system that 
reigned supreme since 1980. Windows 
95 comes with a better DOS than ever, 
but if you are not a DOS lover, it is 

04/23/95 ~ 23:30 - Page I 

d * s*A■ 


possible that you’ll never have to deal 
with a DOS command line and its 
cryptic commands ever again! If you 
are a DOS lover, then you may find 
“hawg heaven ” with MS-DOS 7.0 that 
comes with Windows 95 because you 
can run “pure” DOS as ever, except with 
as many simultaneous “windows” of 
DOS as you like, within limits of reason. 
Other operating systems such as prior 
versions of Windows as well as OS/2 
and certain enhancement programs such 
as DesqView have always been able to 
run multiple instances of DOS but Win 
95 does it the best yet. 

I mention Windows 95 now and will 
periodically do so because a computer’s 
operating system is extremely important 
to the compleat scannist and hacker. 
Win95 offers greatly improved on-and- 
off-line communications, multitasking, 
multithreading, stability, and power, and 
at the same time, is easier to operate than 
any of its predecessors and competitors. 

If you are already into computers and 
computing, you will want to give some 
serious consideration to acquiring Win95 
immediately upon release in August. If 
you know nothing about computers now, 
but may get one in the next few months, 
be sure to wrangle a deal for Win95 on 
that new computer. Don’t get stuck with 
old MS-DOS and old Windows when the 
hot new one is about to come down! 

Windows 95 is specified by Microsoft to 
run on 386DX or better computers, with 
4-Mb RAM (min). One of my Win95 
machines is a 386SX/16, however, where 
it runs ok, albeit a little slow, but it 
always did run slow. The required 4-Mb 
minimum RAM is exactly that, a hard¬ 
core minimum, and the more RAM your 
machine has, the better. Frankly, you’ll 
want to consider 8-Mb as a “productive” 
minimum from which to extract the 
maximum performance that Windows 95 
has to offer. If you can afford it, a 486 or 
better computer is an ideal platform for 
Win95. If you have a 386DX computer, 
that will be ok, too. My kids each have a 
386DX/33 on which Win95 runs just 
fine. The single greatest factor that 
impacts the performance of Win95, aside 
from the type of computer, is RAM. 4- 
Mb is minimum; 8-Mb best for most, and 
16-Mb for heavy duty power users. 

Here, let me show you a screenshot of my 
desktop as I write this section. The 
detail isn’t great because I had to shrink 
down the image to conserve space, but 
you get the idea. Gone are the days of 
old Windows “program groups” and the 
complexity of their installation. 
Everything now runs mostly how you 
want it to run. Yes, you get to choose! 

I prefer to create an icon for most things 
and to double-click them from the 
desktop. There are several other ways, 
one of which will suit most anyone. 
Down at the lower left comer is a button 
called START, from which you can do 
anything, simple and easy like. 


Neither space nor topical dedication 
allows me to pursue the subject of 
Windows 95 much farther now. If future 
interest warrants, I will dedicate a 
column every other month or so to 
Win95 topics simply because computing 
and radio are welded together. Win95 is 
a powerful tool for the compleat scannist 
and hacker, and I would do a disservice 
if I ignored it. 

Radio is poised on the brink of major 
change, and most of that change is 
related to computers. Windows 95 is the 
next generation operating system for the 
downhill run into the 21 st century. It’s 
pertinent. It’s relevant. Stay tuned. © 


Winners from last month’s contest are 
still flowing in, so I’m not going to 
announce them or the results until next 
issue in the offhand chance this issue is 
mailed before April 30, the contest’s 
deadline. I’ve also decided to not 
announce the names of the winners 
unless they so request because of the 
volatile nature of the contest. It occurred 
to me that the target of my little contest 
might vent some anger or other 
retribution to the winners and I would 
never knowingly direct that sort of thing 
away from me onto anyone else. 

Suffice it to say for now that people are 
more attentive than I thought. The 
comments from the winners so far have 
been very heartwarming and interesting. 
More on this next month. 

Next issue (V5N5) will be the last for the 
first half of 1995, and some subscriptions 
will expire with that issue. You may want 
to check your mail label for the expiration 
date and renew early to lock in the old 
rates and to lighten the load on Cindy who 
makes sure everything about your account 
is perfect You can renew for 6-mos, 1 -yr, 
or 2*yrs, at the old rates, through June 
30, 1995, so give it some thought, and 
renew early to avoid missing an issue or 
needlessly having to pay the higher rates 
because you forgot! 

04/23/95-23:30- The “World Scanner Report” © 1991-95; Volume 5, No 4; Page 2 




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PRO-2004/5/6 & PRO-2035 

- Explained - 

Continuing with our circuit analysis 
series, this month we will take a look at 
the main receiver sections of the PRO- 
2004/5/6 and PRO-2035 series. The 
PRO-43 will fit this analysis in some 
ways, too. Schematics and circuit 
symbols as shown will be for the PRO- 
2006, but are readily related to the 
PRO-2004, PRO-2005 and in some 
instances, the PRO-43 because these 
receivers share a lot of common 

The most critical section of any receiver 
is its RF Front End, generally a 
preamplifier with surge and spike 
protection and highly desirable bandpass 
filters. See last month for a detailed 
analysis of the Bandpass Filter section of 
these fine radios. We need not repeat it 
here. But in summary, a signal enters 
tlie receiver from the antenna jack and is 
immediately sensed by DC shunt coil LI 
and protection diodes, D1 & D2. Input 
impedance of the receiver is established 
by the adjustable L-2. 

The RF signal then goes through the 
ATTenuator switch, S-l, and on into the 
bandpass filter network as discussed last 

Out of the bandpass filter network, the 
RF signal goes into a precision designed, 
wideband, low noise preamplifier 
network consisting of transistors, Q3-Q5. 
Q3 and Q4 are emitter followers. 

primarily for impedance matching and 
isolation of Q-5, the main gain amplifier, 
from the antenna and B.P.F. networks. 

Q3-Q5 are critically designed surface 
mount transistors and should never be 
tampered with by any but the most astute 
hackers....and even then...???? 

Out of Q5, the highly amplified RF 
signal goes into a little known circuit 
that separates the men from the boys of 
VHF-UHF scanners: a “doubly 
balanced mixer”, or D.B.M. A real 
class-act, the DBM is a superior device 
or circuit that naturally eliminates 
certain kinds of interference and 
maintains a purity of its output signal. 
The purpose of any mixer is to accept 
two input frequencies and output a 
single frequency. The outputs of most 
frequency mixing processes are the sum, 
the difference, and each of the two input 
frequencies. Inferior mixers of the type 
used in most scanners produce plenty of 
other outputs as well, including phase 
noise and harmonic modulation 
products. The DBM is also a great 
performer under strong signal 
conditions that tend to overload lesser 

The DBM here consists of a special 
sealed Schottky hot-carrier diode pack, 
D30, and is balanced on both its inputs 
and its output by L49 and L48. None of 
these three components should ever be 
tampered by the hacker. 


04/23/95-23:30 - The “World Scanner Report” © 1991 - 95 ; Volume 5 , No 4 ; Page 3 

PRQ-2006 1st IF AMPLIFIER & 2nd MIXER 


Also inputted into the DBM is a local 

one frequency. Read on, McDuff.. 

oscillator (LO) injection frequency from 
tire PLL/VCO section. We’ll cover the 
PLL and VCO at another time, but for 
now, just know that the DBM gets two 
inputs, one from the RF Front End, and 
one from the LO. Obviously, the signal 
from the RF Front End consists of ALL 
frequencies between 25-1300 MHz 
minus those above/below the Bandpass 
Filter networks that are rejected: still, 
there is a boatload of signals inputted to 
tire DBM. The LO signal is a tuned 
signal selected by the CPU based on the 
frequency that appears in the Display. 
Tire range of the LO is 636-1136 MHz 
and 1368-1908 MHz, depending on the 
frequency in the Display. The four 
outputs of the DBM will consist of: 

1. Sum of LO and RF ffeqs 

2. Difference of LO and RFfreqs 

3. LO frequency 

4. RF frequency(ies) 

Four outputs? That doesn’t sound 
healthy, when you want to listen to just 

The four distinct outputs of the DBM are 
fed to narrowband amplifier, Q6, which 
is tuned by resonant circuit, L52, to just 
the narrow range of 607-612 MHz! This 
has the effect of rejecting three of the 
above four signals, leaving ONLY the 
desired signal(s). Actually, a passband 
of desired signals, but considerably 
narrowed from the 25-1300 MHz 
spectrum present at the antenna! 

Sidenote: Getting the picture here yet? 
A huge spectrum of signals comes into 
the receiver via the antenna. The BPF 
network rejects a lot of those signals, 
especially those not in the band of 
interest. (See last month). The RF 
Amplifier amplifies what’s left; mixes it 
with a frequency from the LO and feeds 
four specific freqs or narrow bands of 
freqs to the 1st IF amplifier, which 
further narrows the range of signals that 
can pass through. 

The highly amplified, narrow range of 
frequencies (607-612 MHz) that contain 
the desired signal is fed to the 2nd 
Mixer, Q7, a typical, single-ended 
mixer of no special importance other 
than, like the DBM, it has two inputs 
and an output. The other input is a 
second LO frequency from the 
PLL/VCO section that’s selected by the 
CPU based on the frequency in the 
display. This injection frequency is a 
single frequency between 559-563 MHz. 

Like all mixers, the output of Q7 
consists of four frequencies, sum, 
difference, and each input frequency. 
Once again, selectivity comes into play 
by virtue of tuned device, T-l. Now we 
get into the nitty gritty of receivers. 

Suppose the output of the 1st IF amp 
were 611.5 MHz and that the LO was 
563.0 MHz. Then the output of Q7 
would be four frequencies: 

1. Sum of LO and 1st IF freqs: 1174.5 MHz 

2. Difference ofLO and 1st IF freqs: 48.5 MHz 

3. LO frequency: 563.0 MHz 

4. 1st IF frequency(ies): 611.5 MHz 

Now see what happens if T1 is tuned to 

48.5 MHz? The other three freqs are so 
far off that they are totally rejected! 

48.5 MHz is the output of T-l and is 
then fed to one of two places, depending 
on the Mode ( AM/NFM/WFM) setting. 

If Mode is set to WFM, the 48.5 MHz 
2nd IF signal is sent to 2nd IF amplifier 
Q9, in the WFM section. 

If Mode is set to NFM or AM, the 48.5 
MHz 2nd IF signal is sent to 2nd IF 
amplifier Q15, in the NFM/AM section. 

Since the signal path goes into a “tee”, 
one way or the other, we now have to 
analyze each choice separately. 


If Mode is set to WFM, the 48.5 MHz 
2nd IF signal from Q7/T1 is sent to 2nd 
IF amplifier Q9. Out of Q-9/T2, the 

48.5 MHz signal goes straight into 3rd 
Mixer, Qll, which mixes QlO’s 3rd LO 
of 37.800 MHz, the four outputs of Qll 
which are: 

04/23/95 - 23:30 - The “World Scanner Report” © 1991-95; Volume 5, No 4; Page 4 

1. Sum of LO and 2nd IF freqs: 86.30 MHz 

2. Difference ofLOA 2nd IF freqs: 10.70 MHz 

3. LO frequency: 37.80 MHz 

4. 2nd IF ffequency(ies): 48.50 MHz 

Qll feeds T3, which is tuned to 10.7 
MHz, and which thereby rejects the other 
three undesired signals. 

Sidenote: Regardless of the signals in 
the antenna, by the time the signal 
leaves Q11/T3, it is a fixed 10.7 MHz 
and does not change any further until it 
has been processed by IC-1 into audible 

The Q11/T3 signal goes into a highly 
selective ceramic filter, CF-1, tuned to 
10.7 MHz to further reject noise and 
undesired signals. CF1 feed the 10.7 
MHz 3rd IF signal into IC-1 at Pin 2 
where it is internally processed, and 
outputted at Pin 4 to go through CF2, 
also tuned to 10.7 MHz, for more 
rejection of undesired signals, and then 
back into IC-1 at Pin 6 for final 
processing into audible signals outputted 
at Pin 10. 

We will discuss what happens to audio 
signals from Pin 10 in a future analysis 
of peripheral and control circuits. 

Both : If Mode is set to NFM or AM, the 
48.5 MHz 2nd IF signal output of Q7/T1 
is sent to a sharply tuned prefilter, XF1, 
for rejection of undesired signals, and 
then into 2nd IF amplifier Q15 & Q16. 

Q16 feeds T7 for more tuning of 48.5 
MHz and rejection of undesired signals 
and then goes into IC2 at Pin 18. 

An internal mixer in IC-2 at pin 18 feeds 
by a 3rd LO signal from Pin 1 where 
there is a 48.050 MHz quartz crystal. 
The output of this 3rd Mixer is: 

1. Sum of LO and 2nd IF freqs: 96.55 MHz 

2. Difference of LO and 2nd IF freqs: 455 kHz 

3. LO frequency: 48.05 MHz 

4. 2nd IF frequency(ies): 48.50 MHz 

The 455 kHz 3rd IF is internally 
processed by IC2 and outputted at Pin 3 
to sharply tuned ceramic filter, CF4, for 
massive rejection of undesired signals. 

The output of CF4 splits and goes two 
ways, one back into IC2 at Pin 5 and the 
other up to ceramic filter CF3, at the 
input to the AM section. This “tee” path 
is not a choice like that for WFM and 

NFM/AM, though. Even when the 
receiver is set to the NFM mode, a 
portion of that 3rd IF signal goes 
through the AM section of CF3, Q12 and 
Q13, where an Automatic Gain Control 
signal is developed by D33 for control of 
the gain of the RF Front End. We will 
discuss the AGC and other peripheral 
receiver circuits at a later date. Just 
remember for now that the AM section 
of Q12 and Q13 is used for both AM and 
NFM modes to generate the AGC signal. 

Back to the “tee” at CF4, the other path 
of which goes back into IC2 at Pin 5 for 
final processing into audible signals 
outputted at Pin 9. We will discuss what 
happens to the audio signals from Pin 9 
at a future time. 

AM-onlv: If Mode is set to AM, the 455 
kHz 3rd IF signal in IC2 is outputted at 
Pin3 to and through CF4 for filtering 
and rejection of undesired signals. The 
output of CF4 splits (partly discussed 
previously), one path back into IC2 at 
Pin 5 and the other path to CF3 at the 
input to AM section at Q12. CF3 is a 
highly selective ceramic filter tuned to 
455 kHz and which rejects undesired, 
adjacent signals. 


4/24/95-1-.27PM- The “World Scanner Report” © 1991-95; Volume 5, No 4; Page 5 

The 455 kHz output of CF3 is amplified 
by Q12; timed by T5; amplified again by 
Q13; tuned again by T6; then fed to 
AM/AGC detector diode, D33, and 
filtered into a varying DC (audio!) by 
C160. The output of D33 splits, one 
path going on to AGC control circuits (to 
be discussed later) and the other path 
through Automatic Noise Limiter diode, 
D34. The output of D34 is an audio 
signal. We will discuss what happens to 
signals from D33 and D34 in a future 
article on peripheral and control circuits. 


RF signals from the antenna are 
prefiltered in the BandPass Filters; 
amplified by Q3-5; mixed at D30 by a 
local oscillator signal from PLL1 and 
converted into the 1st Intermediate 
Frequency of 607-612-MHz and 
amplified by Q6. The 1st IF signal is 
mixed in the 2nd Mixer by a 559-563 
MHz LO signal from PLL2 and 
converted into the 2nd IF frequency of 
48.5 MHz and amplified by either Q9 
(WFM) or Q15 (NFM/AM), depending 
on tlie Mode setting of the receiver. 

The WFM 2nd IF signal is mixed in Q11 
by a 37.8 MHz signal from Q10, the 
output of which is 10.7 MHz and fed to 
the WFM chip, IC1 for final processing 
into audio signals at Pin 10 of IC-1. 

The NFM/AM 2nd IF signal is amplified 
by Q15 & Q16 and fed to a mixer 
internal to IC2 at Pin 18. The 48.05 
mixing signal is generated by X2 and fed 
into IC2 at Pin 1. where the internal 3rd 
IF 455 kHz signal is produced, 
amplified, and outputted to CF4 to Pin 3 
of IC1. CF4 feeds the 455 kHz 3rd IF 
back into IC1 at Pin 5, but also up to 
CF3 for amplification byQ12&Q13. 

NFM signals are processed by IC1 and 
converted to audio at Pin 9. AM signals 
are detected by D33 and noise limited by 
D34 and fed to audio preamp, Q18. 

NFM & AM Automatic Gain Control 
(AGC) for the IF and RF amplifiers is 
generated by D33 and distributed in a 
path that will be discussed in a future 
article. WFM mode does not use AGC. 

Selectivity of the scanner’s WFM mode 
is partly set by T3 and CF1 and polished 
off to 150 kHz by CF2. The center of the 
WFM Discriminator curse is set by T4 
with the baseband & audio output at IC1, 
Pin 10. 

Selectivity of the NFM and AM modes is 
partly set by XF1 and T7. CF4 shapes 
the 15 kHz selectivity curve for NFM- 
only signals and partly for AM signals. 
AM selectivity is set at 6 kHz by CF3. 
The center of the NFM Discriminator 
curve is set by T8, with the baseband and 
audio output at IC2, Pin 9. 

The foregoing analysis is expressly for 
the PRO-2006, but is matched almost 
identically by the PRO-2005. The PRO- 
2035 is a second close match except that 
some of the circuit symbols differ from 
that mentioned herein. As an example, 
the DBM in the PRO-2035 is D31. The 
PRO-2004 is also the subject of this 
analysis, but there are a number of 
design and circuit symbol differences 
such that it may be difficult for the 
neophyte to follow this discussion on a 
PRO-2004 schematic. 

For the PRO-2004, PRO-2005 and PRO- 
2035, it is strongly suggested that you 
have a schematic of the PRO-2006 to 
hold up against the one for your scanner 
so you can follow the discussion, and you 
will, because these four radios are really 
very much alike. 

IF YOU NEED A SCHEMATIC diagram of the 
PRO-2006 for this (or any other ) purpose, I will be 
happy to prepare a nice one for you for a handling 
fee of $5— plus a double stamped, self-addressed 
envelope of your choice. The schematic consists of 
two double-sided 11 x 17 sheets and one SVi x 11, so 
at least send me a double-stamped #10 business 
envelope with the five bucks. Note these are nicely 
done schematics, so you may want to provide me with 
a 9x12 manila envelope. If you don’t want to provide 
the double postage and envelope , then the handling 
fee is $?— ppd., and I’ll provide a manila envelope. 

By Gregory K. Doerschler 

ED: The term “Zeromatic” used in 
Greg's article is a trademark by the 
Tandy Corporation. 

The Realistic PRO-2006 scanner 
incorporates " Zeromatic tuning " in the 
Search mode. When a signal is 
detected, Zeromatic keeps Search from 
stopping prematurely on an adjacent 
frequency by holding the SQuelch 
closed until the signal is center tuned. 
With a simple mod, the Zeromatic 
tuning circuit can be activated in Scan 
and Manual modes as well. In these 

modes, the circuit can SQuelch splatter 
from strong adjacent channel signals as 
well as any images or stray signals that 
are more than a few kHz off-frequency. 

The idea for this mod came as a result of 
my search for elusive low power signals 
on 12.5 kHz “split”" channels in the 
461465 MHz band. With the PRO-2006, 
there is no way to Search these freqs 
without hitting the standard 25 kHz¬ 
spaced business channels as well. (For 
instance, you can't Search 461.1125 and 
461.1375 MHz without also hitting 
461.125 MHz.) Activity on the 25 kHz 
channels was so heavy that I missed most 
of the elusive stuff on the split freqs. 

When I installed the 6400 channel 
memory mod in my 2006, I decided to 
program all of the 461465 MHz split 
freq allocations in dedicated memory 
banks so I could Scan them exclusively, 
rather than use the Search function. 
The problem with this plan was that 
adjacent channel splatter from very 
strong signals on the standard 25 kHz 
channels would often lock up the Scan. 
Realizing that adjacent channel splatter 
did not cause problems in the Search 
mode because of the Zeromatic tuning 
circuit (which holds the SQuelch closed 
until the Search stops on the actual 
transmission frequency), I surmised that 
activating the Zeromatic circuit in the 
Scan and Manual modes would also 
keep adjacent channel signals from 
breaking SQuelch in these modes. 

IC4 on the main PC board of the 2006 is 
at the heart of the Zeromatic circuit. 
When the frequency error of an 
incoming signal exceeds the Zeromatic' s 
tolerance, a high output will be present 
at either pin 7 or 8 of IC4. In the Search 
mode, this output is fed to pins 5 and 6 
of IC3 (which functions as an inverter); 
producing a low output at pin 4. This 
output and the receiver SQuelch gate 
output at IC2 pin 13 are fed to pins 2 and 
1 of IC3 (a NAND gate) respectively. 

The output of this NAND gate (pin 3) is 
the SQuelch signal which is sent to the 
CPU via the "SQ" line at pin 5 of CN3. 
A low output means an open SQuelch, 
and the CPU stops the Search. Since 
this output will be low only when both 
inputs (pins 1 & 2 of IC3) are high, the 
Search will not stop unless (A) a high 
input at pin 1 is present due to an open 
receiver SQuelch and (B) a high input at 

4/24/95- 1:47PM- The “WorldScanner Report’ 9 © 1991-95; Volume 5, No 4; Page 6 

pin 2 is present, which occurs when the 
incoming signal is tuned within the 
Zeromatic circuit's frequency tolerance. 

The frequency tolerance of the Zeromatic 
circuit varies depending upon the Search 
step. When SEARCHing in 5 kHz steps, 
+5 volts is supplied by the CPU on the 
5kHz line, which runs to the Zeromatic 
circuit via CN3 pin 7. This results in a 
tighter frequency tolerance when 
SEARCHing in 5 kHz steps than when 
SEARCHing in 12.5 or 50 kHz steps. 
(This makes sense since your closest step 
will always be within 2.5 kHz of the 
actual frequency when SEARCHing in 5 
kHz steps, but may be as much as 6.25 
kHz off frequency when SEARCHing in 

12.5 kHz steps.) For the remainder of 
this article, I will refer to these two 
frequency tolerance settings as the 
Zeromatic "narrow" and "wide" settings. 

When the scanner is not in the Search 
mode, the Zeromatic outputs at IC4 pins 
7 & 8 are diverted to ground via IC3 pin 
10, effectively disabling the Zeromatic 
circuit. IC3 pin 10 is the output of an 
inverter, which receives its input signal 
on pins 8 & 9 from the CPU via the 
"SEARCH" line (CN3 pin 6). The CPU 
supplies +5 volts on the SEARCH line 
whenever the scanner is not in the 
Search mode. It is this signal that turns 
off the Zeromatic circuit. 

There are several ways the 2006 can be 
modified to activate the Zeromatic circuit 
in the Scan and Manual modes. The 
circuit can be used in the wide setting or 
the narrow setting, or made switchable 
between the two. A switch which turns 
the circuit off entirely may also be added 
for those times when you'd want to be 
able to hear off-frequency signals (such 
as when you're trying to identify them). 

The wide and narrow Zeromatic settings 
do a comparable job of SQuELCHing 
adjacent channel transmissions, but the 
narrow setting does a better job of 
SQuELCHing images and other 
interfering signals which are only 
slightly off freq. For instance, I find that 
it effectively SQuelchcs many of the 
cellular telephone images which I receive 
in the aircraft band when they do not fall 
directly on the programmed frequency. 

The disadvantage of the narrow setting is 
that some desired transmissions could 
also be SQuELCHed if they are a bit off- 
frequency or if the scanner is not 

programmed to the exact transmit 
frequency. This could especially be a 
problem for scanners that are subject to 
temperature extremes (such as in a 
mobile environment) where the internal 
oscillators would be more apt to have 
shifted somewhat over time. Using the 
narrow Zeromatic setting, a signal only 

1.5 kHz off frequency would not be heard 
if the scanner's oscillator had also drifted 

1.5 kHz in the opposite direction. The 
wide Zeromatic setting is sufficiently 
forgiving for this not to be a concern. I 
use the narrow Zeromatic setting 
exclusively in my 2006 and have not 
encountered any problems, but it is 
important to be aware of the potential. 

To measure the tolerance of the two 
Zeromatic settings, I swept a strong, 
unmodulated carrier across the scanner's 
programmed frequency with Zeromatic 
tuning in the narrow, wide and off 
settings (using the NFM mode). The 
carrier broke SQuelch over a range of 
approximately ±2.8 kHz with the narrow 
Zeromatic setting, ±5.1 kHz with the 
wide Zeromatic setting, and ±9.0 kHz 
with the Zeromatic tuning turned off. A 
modulated carrier takes on a "fuzzy," 
chopped-up sound if centered exactly on 
the Zeromatic tuning's tolerance limit, 
and disappears altogether quite abruptly 
when centered just beyond the limit. 
With the Zeromatic tuning turned off, a 
modulated carrier would produce splatter 
on voice peaks when centered beyond the 
±9.0 kHz limit (as previously discussed). 

The easiest form of this mod is to hard¬ 
wire the Zeromatic tuning circuit to be 
operational full-time in the wide setting. 
Clip the brown wire from CN3 Pin 6 on 
the main board about midway, and 
connect the CN3 side to ground through 
a 10K resistor. (CN3 is a 15-pin 
connector located on the front edge of 
the main PC board.) If you have the Key 
Research PS-90 “Search & store” mod 
in your scanner, you will have to remove 
the white wire connected to IC-3 pin 8 
and reconnect it to the clipped brown 
"SEARCH" wire running to the CPU 

Figure 1 illustrates how to make this 
mod switchable using a SPDT switch. 
Note that the Zeromatic function will 
continue to operate in the Search mode 
regardless of the position of the switch, 
and will still revert to the narrow setting 
when SEARCHing in 5 kHz steps. 

To activate the narrow Zeromatic setting, 
perform the above wide Zeromatic mod 
(preferably with the switch). Install a 
NPN switching transistor (2N2222A) as 
shown in Fig-2. D47 is on the main PC 
board behind CN3. The cathode is the 
top lead. If you're good at working in 
relatively tight places, solder the emitter 
of the transistor directly to D47 and 
solder the collector of the transistor to 
the pad on the PC board directly behind 
CN3 pin 3; next to D47. This is a source 
of +5 volts. Other accessible sources of 
+5 volts include the output (rear-most 
lead) of voltage regulator IC8 on the left 
edge of the main PC board, and IC3 pin 
14 on the main board. 

The base lead of the transistor gets wired 
to the center pin of your SPDT 
"wide/narrow" switch. If you only want 
the Narrow Zeromatic setting without 
the ability to switch to Wide, omit the 
switch and 10K resistor and connect the 
transistor's base directly to the clipped 
brown SEARCH wire leading to the CPU 
board. I consider this switch to be a bit 
frivolous as long as you have the 
Zeromatic on/off switch, but it is your 
choice if you want to include it When 
the scanner is used in the Search mode, 
the NPN transistor is turned off and the 
wide/narrow Zeromatic selection is 
determined by Search step. Neither the 
Zeromatic on/off switch nor the 
wide/narrow switch will affect the 
Search mode. 

I installed a DPDT switch for the 
Zeromatic "on/off" switch in my 2006 
instead of a SPDT switch, and used the 

4/24/95-1:52 pm~ The " World Scanner Report” © 1991-95; Volume 5, No 4; Page 1 

NOTE: This is a simplified diagram of 
I the PRO-2006 Zeromatic circuit that 
really requires benefit of the Service 
Manual for full understanding. Do not 
| fail to acquire one for your scanner. 
There are minor differences among the 
PRO-2004/5/6/2035 (800)442-2425 


-O R#d ^ SQuvIch 

> To CN3 Pin 6 
(Set Figure 3) 

second set of switch contacts to engage 
a manual tuning mod. This was 
accomplished by clipping the red SQ 
wire running from the CPU board to 
CN3 pin 5 midway and splicing in the 
switch as shown in Figure 3. 
Essentially, when I turn off my 
Zeromatic tuning, this second set of 
switch contacts sends an "open 
SQuelch" signal to the CPU; regardless 
of whether a signal has actually broken 
the SQuelch. This prevents the scanner 
from SEARcmng or scanning since it 
thinks it’s hearing a signal. I can then 
enter a frequency into any channel, push 
the DIRECT key, and use the 
UP/DOWN keys to manually tune up or 
down from the frequency I entered; 
similar to a tuning knob. This is the 
one time when I definitely want 
Zeromatic turned off in order to hear 
off-freq signals as I approach them. 

The manual tuning mod can also be 
performed or controlled independently 
of the Zeromatic tuning mod. 
Combining the two on a single switch 
was a practical consideration for me. 
With ten toggle switches and two jacks 
I'd already added to the back of my 2006, 
available real estate was getting pretty 


Red "SQ” Wire 

To CPU Board 

0 — i 
“0 -> _ 

Switch shown in 

Manual Tuning Off 
Zeromatic "On" 

Red "SQ" Wire 

ToCN-3, Pin 5 


To test the Zeromatic mod, find a very 
strong local signal and punch in a 
frequency 10 kHz away from it (or 5 kHz 
away, if you're using the narrow 
Zeromatic setting). Open the SQuelch 
by turning the SQuelch control fully 
counterclockwise. Whenever the strong 
local signal transmits, the SQuelch 
should close; silencing the speaker. 
With the Zeromatic tuning turned off, 
you should hear splatter from the signal. 

You can actually demonstrate this effect 
without even performing the mod. Enter 
a frequency 10 kHz away from a strong 
local signal, on which you can hear 
splatter when the local signal transmits. 
Then enter that frequency as both an 
upper and lower Search limit and go 
into the Search mode. The Search 

range will be limited to just the one 
frequency and the Zeromatic tuning will 
be on, so the splatter will not be heard. 

I do not believe that there are any 
negative side-effects to the Zeromatic 
mod. If you encounter an off-freq or 
adjacent channel signal while scanning 
with Zeromatic engaged, the Scan may 
sometimes pause silently for an instant 
on either the affected channel or the next 
channel in the Scan sequence. Without 
the Zeromatic tuning though, the Scan 
would stop and you'd be listening to the 
interfering signal; so it's really not an 
annoyance by comparison. 

Those who have performed the automatic 
tape recorder switch Mod-33 or the 
carrier indicator mod from Vol-2 of the 
Scanner Modification Handbook may 
notice the relay or LED indicator 
momentarily click "on" even though 
audio is not present and the Scan does 
not stop. This is due to the fact that these 
mods take their SQuelch signal directly 
from the receiver SQuelch gate at IC2, 
and they will sense when an off- 
frequency signal breaks the SQuelch 
even though the Zeromatic tuning 
prevents the open SQuelch signal from 
being sent to the CPU. 

Understand that Zeromatic does not 
actually improve the selectivity of the 
scanner. Offending off-freq or adjacent 
channel signals are "ignored" by the 

scanner, but they are still present in the 
circuit and could mask weaker, desired 
signals. Nevertheless, my Zeromatic 
Mod allows channels to be scanned that 
otherwise would probably be locked out 
because of interference. © 

ED COMMENT: Greg did a hell of a 
job on this article; my hat’s off to ‘im! 
Wish I had developed it myself Well I 
get to help anyway. Greg didn’t have 
the resources to identify the differences 
among the PRO-2006, PRO-2005, and 
PRO-2004, so follows my list of those 
differences. This Zeromatic Mod will 
work with these three scanners and 
maybe others with similar Zeromatic 
tuning circuits. The PRO-2035 differs 
enough that an altered procedure will be 
covered in a future article . A quick 
exam of the PRO-43 reveals a Zeromatic 
circuit similar to the PRO-2035 *s so stay 
tuned for more. Perhaps Greg and I can 
work up the mods for other Realistic 
scanners, too. Sorry, Uniden scanners 
are much too different for this mod. 



CN-3 Pin 5 


CN-3 Pin 6 

5 kHz Step: 

CN-3 Pin 7 



CN-3 Pin 5 


CN-3 Pin 6 

5 kHz Step: 

CN-3 Pin 7 



CN-504 Pin9 


CN-504 Pin 10 

5 kHz Step: 

CN-504 Pin 14 

4/24/95-1:54 PM ~ The “ World Scanner Report” © 1991-95; Volume 5, No 4; Page 8 


From: Burleson D. White, Beachwood, OH 

Are you planning to review the AOR AR- 
8000 AR-8000? Is it modifiable? Why not 
use the CE-232 computer monitor screen to 
replace the dead PRO-2004/5/6 EL display? 

ED : AOR scanner series are marketed by a 
firm that does not cooperate with or respond 
to our requests for technical information. 
Furthermore, AR Service Manuals suck 
rocks. On that basis, I do not buy AR 
scanners and therefore never have one in 
hand to review unless someone gives or loans 
me one. So far, that hasn ’t happened. 

The CE-232 certainly offers a superior 
display to that of any scanner, but it is rather 
expensive for a “ replacement © By the 
way, the EL panel in these scanners is a 
backlighting panel; not the actual LCD 
display module. I have never seen a display 
fail unless it was physically broken. The EL 
panel slides behind the Display module. 

From: William Shaft. Tinlev Park, IL 

Doc, Doc: Send me the news. Willie Shaft 
here has a new PRO-2035 and needs the 
Ultimate Scanner to find out what to do. I 
have Scanner Mod’s Vol 1 & 2 and have 
hacked the PRO-2004/5/6 and the PRO-34. 

The PRO-2004 will always be my favorite 
because of the nice angle, touch keyboard 
and metal case. Thanks for the advice 
warning that the Tandy dorks make parts not 
available for the PRO-2004. Until I see your 
book, the solder sucker and iron will stay 
ready. P.S. I love listening to all the Adam 
Henry’s with car phones. Wireless shouldn’t 
be private. 

ED : The PRO-2035 proves hackable, along 
the lines of the PRO-2004/5/6, since it is 
much the same scanner, electrically. The 
Ultimate Scanner offers a good start and the 
WSR will continue its enhancement and 
development. I agree that it’s downright 
ignorant of Congress to legislate privacy of 
the airwaves. That’s no different than 
legislating privacy of conversations in 
restaurants, workplaces, public parks, and 
on the sidewalks! Good grief! 

From: Arthur Zepeda. Visalia. CA Dear 
Bill, I’m not much for writing letters, but 
you’ve got to read my story. I’m going on 28 
years of age. I have a high school diploma 
and also an A.S. Degree in automotive repair. 
I’m currently going on six years working for 
the school district in Visalia and about one 
year as a night lead custodian (janitor, for 
those who work for the government. HA!). 
Prior to that, I spent four years in the Army as 
a Chaparral missile crewman. Aside from 
Basic and ATT, I was stationed at Ft Ord the 
whole time. 

So where is my electronic experience you 
might ask? There really isn’t any. Aside 
from the electronic aspect of a car, they just 
teach you to find and repair. 

So, I have a PRO-2006/43/51 and a 22. No, 
not caliber, an old 6-ch crystal (yard sale $5). 
A lot of $$$ plus $25 to have someone 
“install” cellular frequencies. Hmmm. When 
I purchased the PRO-43 (first scanner), oh, 
by the way, I just didn’t start off with the 43, 
but that’s another story. Anyway, not even in 
my wildest dreams did I ever think I would 
open and do the cell mod to the 43! I’ve 
never even used a soldering gun on those 

delicate electronic components! Then.I 

saw your two books in a Grove catalog. “I’ve 
got to have those,” I said to myself. 

I was visiting some friends in San Carlos, 
CA, and we went to a shop called “ Scanners 
Unlimited.” Cool shop, by the way. Nothing 
like it where I’m from (40 miles south of 
Fresno). I purchased Book 2, and was amazed 
at how simple y ou made everything seem. 

I started with the C.O.I., Mod 32 on the 
2006, and you betcha, I was proud. Next 
came Mods 26 & 27. Big head now! Then 
came the WSR, Book 1 and back issues of the 
WSR. That’s when the 43 went on the 
operating table for the cell mod. This, of 
course, was my first job dealing with SMT. 
Wow! My eyes still hurt! 

And, just as I’m writing this letter, UPS lias 
just delivered the stuff for the 25,600 channel 
and mod 28 from JDR Microdevices!!!! 

The bottom line is this. Thank you Bill for 
making it easy for me to add another 
dimension to my monitoring hobby! I look 
forward to adding your third book to my 
library! Try to keep up the good work. I 
realize it’s getting harder to hack because of 
firmware but you can deal with it. Take care 
and God bless you and your family! PS I 
actually paid someone to clip two diodes on 
the 2006! Man! 

ED : Thanks for your story. I often wonder 
how people get started. There were many 
turning points in my life starting with a 
transistor radio for my 12th birthday in 
1957. 1 opened the back of the case and 

poked around on the solder joints with the 
end of a 100-ft longwire. Suddenly stations 
roared in, including HCJB in Quito, 
Ecuador, with an Armed Forces Day 
program. Hooked! Some years later, 1 got 
ripped for a $50 repair bill on a funky old 
CB radio. That got me started on working on 
my own stuff. The FCC busted me in 1987 
which started me in earnest on scanners. The 
rest is history. Do keep us posted! 

4/24/95~2:oo pm ~ The “World Scanner Report” © 1991-95Volume 5, No 4; Page 9 

1 iiSiii^iSiiiiiSi^S 


USA RATES shown: Canada add 15%: Other Foreign +25%-surt/+50%-Air 



1991 (1st Year, Jan-Nov/Dec) - lOea $20.00 


1992 (2nd Year, Jan-Nov/Dec) - 10 ea $21.00 



1993 (3rd Year, Jan-Nov/Dec) - 10 ea $23.00 

1994 (4th Year, Jan-Nov/Dec) - 10 ea $25.00 



Work Ph: ( ) - Career or 


Home Ph:( ) - Profession 

1mm • 


& Other Radios » 

Half Year 5 ea $15.00 

One Year lOea $25.00 

METHOD OF Check Cash M.O. Visa MstCard COD (+$8.50) 
payiuifnt » n n n n n 

Amount Enclosed 


Two Years 20 ea $45.00 

Credit Card 

Acc't No: » - 

Amount Charged 

Scanner Mod Hndbk, VoM : $17.95 + $4.00 S&H * 
Scanner Mod Hndbk, Vol-2: $17.95 + $4.00 S&H * 

Name of Expiration / 

Ultimate Scanner til 6/30/95 $24.95 +$4 S&H * 
Scanners & Secret Frequencies $19.95 + $4 S&H * 

Issuing Bank Date: 


Signature Required (for credit card purchases) 


|( | 

* Canada USS7 S&H; Other Foreign US$9 S&H; Air extra 

CE-232 Interface Kit $194.95 + $5 S&H: All Foreign add 25%-surf 

VISA !| 

.. 1 

Calif reaidenta: Sale* Tax - 7.0% on all orders except WSR subs 

What else to tell us? 

r ^pi 

I Master 


From: Paul Longo, Stamford, CT Your 
observations in V5N3 of the WSR are, as usual, right 
on the mark. It seems that form has superseded 
function in everything. How many restaurants have 
you gone to in which you find opulent decor, 
mediocre food and lousy service? Looks like the 
yuppies put more value on how things (or people) 
look rather than how well they work. The “empty 
shell syndrome” creeping into new scanners is a spin¬ 
off of the “empty suit syndrome” that now runs 
rampant in corporate America. (When are we going 
to lose these people,?) 

ED : We’re not, Paul. Look back 500-yrs and see 
how “backward” people were? Well 500-yrs from 
now, they’ll be looking back and chuckling at how 
backward we were. But us Hackers will be their 
revered ancestorsI 


From: Tony Thornton, Mize, MS Bill, do you 
know of a source for NMH batteries with a better 
price than the $7.00 each that Metro West wants for 
them. I’ve looked in various catalogs such as “Digi 
Key” and others, but haven’t found any listed. I’ve 
seen the mfgr’s ads in a couple of trade magazines, 
but found no source but Metro West. I’ll pay the 
$7.00 if I have to but would like to think they’re 
available cheaper than that Keep up the good work. 
(Can a NI cad charger be used with them?).thanks. 

ED : A recharger is a recharger, but designs must 
be optimized, else you ’ll overcharge or 
undercharge. I’ll do an article on the subject soon, 
since that’s an important topic. You can check the 
following company, but I have no clue on their 
prices. Tell ’em we sent ya. 

Alexander Battery Co; PO Box 28880, 
San Diego, CA 92198; (800) 327-0814 

displayed. “PRIVATE” calls don’t get answered here. 
Also, certain social agencies have an automatic Caller 
ID block on their phones (places like battered 
women’s shelters, etc). 


Now I have just one question for you. Where is the 
discriminator point on the PRO-43 radio? I want to 
run a line from there to a jack, so I can plug in a 
PL/DPL reader into it, and I need the point where the 
signal can be picked off before it is stripped in the low 
pass filter. If you have time, could you post it to me 
in the Internet at DARYLLI@AOL.COM. Thanks! 
I’ll be waiting for your new book. 


If I were you, I’d solder a 2.2-pF/16v capacitor, (+) 
lead to Pin 9 or TP-201 and take your output ojf the 
(-) lead. That will protect the chip and still pass 
plenty of signal to your PL device. Remove the rear 
case of the PRO-43 and you should see Pin 9 
staring up at you as shown in the graphic. 

Thanks for the added info on Caller W. I don’t 
know much about it yet since Calif doesn ’t allow us 
to have it. The Ultimate Scanner looks to be 
available on or about May 1, now so hang loosef 



From: Darvll Symington, Holland, OH I n the last 
WSR, there was a discussion on Caller ID. In Ohio, 
Caller ID will not transmit the number of any phone 
subscriber that already has an unlisted number. Only 
“PRIVATE” will show. Ail callers can block Caller 
ID by dialing *67 before each call. That way, the 
caller can choose if he/she wants their number 

ED : How about both ways, here and via the 
Internet? This way helps others, too. I’ll even draw 
ya a picture so there can be no mistake. The 
discriminator chip differs little from one scanner to 
the next, though the chip numbers, pin counts, and 
styles may very widely. In the PRO-43, it’s IC-301, 
Pin 9, a TK-10427 or TK-10420 surface-mount 
chip. Pin-9 is also TP-301, one and the same point. 

Hey guys ‘n gals, I need your help for my 
next book. The Ultimate Scanner opens 
doors for endless opportunity to write, but 
what do I wile about next? My publisher 
and I are considering a series of detailed, 
moderately priced manuals, each dedicated to 
one particular scanner with a boatload of 
mods & hacks just for that rig. 

Ok, so which do I do first? Second? Third? 
Why don’t YOU dear WSR readers vote to 
give me a sense of direction for the first ones. 
Then, I’ll let the buyers of the series vote on 
subsequent works. OK, here is what I want 
you to do: Use whatever is best for you: US 
mail, fax, e-mail, CompuServe, BBS, or even 
voice phone....just tell me your first three 
choices of make and model of scanner for me 
to write about. Please write “ VOTE 9 on the 
outside of envelopes, or on the subject line of 
e-mail, fax, and BBS messages. List your top 
three picks in order. There is no deadline, 
but the sooner, the better, for obvious 
reasons. I’ll compile results and make a 
tentative decision by July 1 and maybe start 
work in earnest in August. 

My e-mail, CIS-Compuserve, BBS, Fax, and 
phone info are in the Reference Information 
box at the top of Page 1. Drop me a line with 
your guidance for my next book, oo 


04/23/95-23:30- The “World Scanner Report” © 1991-95; Volume 5, No 4; Page 10 




: * 


• " • 

me' ' »... • 

. : & ' * 

PO BOR 262178 

-V* / 

A. • - • 


SAN DIEGO, CA 32106-2178 



Check Your Expiration Date on the Mail Label Below! 


+ Subscription Rates Going Up ~ Ultimate Scanner book still a great bargain 
+ Contest last month doing great ~ Some Subscriptions Soon to Expire 
+ PRO-2004/5/6/2035 Receiver Circuits Explained ~ Mixers, IFs, NFM/AM 
+ Zeromatic Tuning Control for PRO-2004/5/6 ~ A Feature Mod! 

+ Need a clean set of schematics for your PRO-2006? 

+ Why we don’t mess with AOR Scanners ~ EL Panel tidbits 
+ PRO-2035 Hack Future ~ A new hacker’s story: Arthur Zepeda 
+ Editor’s historical brief ~ “Empty Shell Syndrome” 

+ NiCd & NMH battery source ~ More on Caller I.D. 

+ PRO-43 Discriminator Output ~ VOTE on my next book(s)